This paper presents a rigorous, semi-analytical solution for the drained cylindrical cavity expansion in transversely isotropic sand. The constitutive model used for the sand is the SANISAND-F model, which is developed within the anisotropic critical state theory framework that can account for the essential fabric anisotropy of soils. By introducing an auxiliary variable, the governing equations of the cylindrical expansion problem are transformed into a system of ten first-order ordinary differential equations. Three of these correspond to the stress components, three are associated with the kinematic hardening tensor, three describe the fabric tensor, and the last one represents the specific volume. The solution is validated through comparison with finite element analysis, using Toyoura sand as the reference material. Parametric analyses and discussion on the impact of initial void ratio, initial mean stress level, at-rest earth pressure coefficient and initial fabric anisotropy intensity are presented. The results demonstrate that the fabric anisotropy of sand significantly influences the distribution of stress components and void ratio around the cavity. When fabric anisotropy is considered, the solution predicts lower values of radial, circumferential and vertical stresses near the cavity wall compared to those obtained without considering fabric anisotropy. The proposed solution is expected to enhance the accuracy of cavity expansion predictions in sand, which will have significant practical applications, including interpreting pressuremeter tests, predicting effects of driven pile installation, and improving the understanding of sand mechanics under complex loading scenarios.

Non-Darcy seepage can more accurately quantify the bearing capacity of jacked piles during the bearing and reconsolidation processes. This paper is divided into three parts. Firstly, it theoretically analyzes the pore water pressure distribution in the soil around the pile through differential treatment of the equation. Secondly, it simulates the pile sinking process and the reconsolidation process of the soil around the pile after sinking by ABAQUS, and then a parameter analysis is conducted. Finally, a time analysis of the pile bearing capacity is conducted. The results show that the dissipation rate of excess pore water pressure (EPWP) and the consolidation rate of the pile side will be underestimated at the initial stage of consolidation if the influence of non-Darcy seepage is ignored, while the opposite is true in the later stage. The strength and effective stress of the soil are greatly improved in the early stage of consolidation, and the bearing capacity of the static pressure pile is also significantly enhanced. In the later stage of consolidation, as the excess pore pressure of the soil around the pile slowly dissipates, the bearing capacity of the static pressure pile also increases steadily. This paper studies the dissipation of EPWP to make the design of pile foundation bearing capacity more rational and to improve the economic benefits.

Tower foundation plays an important role in transmission line engineering, but the traditional tower foundation has low bearing capacity against uplift and is damaging to the environment. In this regard, this paper proposes a new type of foundation structure, vertical-inclined combined high-pressure rotary piles, and its bearing performance and force mechanism are studied through modeling experiments. (1) The inclined pile inclination angles of 10 degrees and 20 degrees for vertical-inclined combined high-pressure rotary piles increased the ultimate bearing capacity of uplift resistance by 16.29% and 60.31% than that of corresponding vertical piles. (2) After changing the vertical piles into inclined piles, the vertical-inclined combined high-pressure rotary pile foundation can mobilize more soil to resist the vertical load, thus increasing the uplift capacity. (3) Having proposed a formula for calculating the uplift bearing capacity of a vertical-inclined combined high-pressure rotary piles foundation, model test results are also used to verify the formula's accuracy.

To investigate the effects of the maximum principal stress direction (theta) and cross- shape on the failure characteristics of sandstone, true-triaxial compression experiments were conducted using cubic samples with rectangular, circular, and D-shaped holes. As theta increases from 0 degrees to 60 degrees in the rectangular hole, the left failure location shifts from the left corner to the left sidewall, the left corner, and then the floor, while the right failure location shifts from the right corner to the right sidewall, right roof corner, and then the roof. Furthermore, the initial failure vertical stress first decreases and then increases. In comparison, the failure severity in the rectangular hole decreases for various theta values as 30 degrees > 45 degrees > 60 degrees > 0 degrees. With increasing theta, the fractal dimension (D) of rock slices first increases and then decreases. For the rectangular and D-shaped holes, when theta = 0 degrees, 30 degrees, and 90 degrees, D for the rectangular hole is less than that of the D-shaped hole. When theta = 45 degrees and 60 degrees, D for the rectangular hole is greater than that of the D-shaped hole. Theoretical analysis indicates that the stress concentration at the rectangular and D-shaped corners is greater than the other areas. The failure location rotates with the rotation of theta, and the failure occurs on the side with a high concentration of compressive stress, while the side with the tensile and compressive stresses remains relatively stable. Therefore, the fundamental reason for the rotation of failure location is the rotation of stress concentration, and the external influencing factor is the rotation of theta. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

The critical normalized roughness (Rcr) serves as a pivotal metric for distinguishing the roughness of the soil-- structure interface. The accurate determination of Rcr is highly important in both research and engineering applications related to the mechanical properties of the interface. However, research on methods for determining Rcr are scare, and the theoretical methods are especially rare. This paper aims to establish a theoretical calculation method of critical normalized roughness Rcr. Using tribology theory, the existence of Rcr was corroborated through the analysis of both single-particle sliding and whole-soil sliding mechanisms. A theoretical formula was subsequently established for the computation of Rcr. A comparison between the theoretical calculations and experimental results revealed that the proposed formula is applicable to both scenarios involving particle breakage and scenarios lacking particle breakage at the interface. Compared with scenarios without particle breakage, the theoretical formula exhibits a superior predictive capacity for cases involving particle breakage. The proposed theoretical calculation method in this paper provides a novel approach and perspective for determining the critical normalized roughness Rcr.

Layered structure in sand deposits is prevalent not only in reclaimed soils but also in natural alluvial soils. Liquefaction tests by a self-developed impact load system were carried out to investigate the excess pore water pressure (EPWP) generation and related liquefaction mechanism in layered sands, considering cases of uniform, two layered and interlayered sand columns respectively. Results show that the EPWP of saturated sands under impact loading presents two phases: transient response and steady-state response. For sands without interlayer, lower-permeability soil layer determines the rate of EPWP dissipation and lower permeability can result in smaller value of steady pore pressure but longer duration of that. For interlayered sands, presence of less permeable interlayer will prolong the total duration of pore pressure dissipation, and there is a significant high pore pressure sustained period during the dissipation stage of pore pressure, which is unfavorable for the liquefaction. Also, the presence of a less permeable interlayer within the sand deposit can lead to formation of water film underneath the interlayer. Besides, theoretical analysis of EPWP and water film under the same conditions are made, and it shows a good consistency between theoretical and test results, which verifies the rationality and reference value of the test analysis in this paper.

Multiple fault planes often coexist within a fault zone during fault dislocation. However, all the previous analytical models assume that there is only one fault plane during a fault dislocation, which is inconsistent with the actual engineering conditions. In this paper, theoretical analysis and numerical simulations are used to investigate the mechanical response and damage characteristics of tunnels subjected to multiple normal faulting. A nonlinear theoretical model is established for analyzing the mechanical response of tunnels subjected to multiple normal faulting. The number of fault planes, the shear effect of the soil and the tunnel, the fault zone width, and the nonlinear soil-tunnel interaction are applied inside the theoretical model, significantly improving the analysis accuracy and applied range. The corresponding numerical simulation based on the Concrete Damaged Plasticity (CDP) Model is carried out to study the damage characteristics of the tunnel. The proposed theoretical model is verified by model tests and numerical simulations, which exhibit consistency in both qualitative and quantitative aspects. A parametric analysis is presented, wherein the impacts of varying numbers of fault planes, fault plane distances ( d ), fault displacement ratios ( xi ), and buried depths ( C ) on the tunnel response are investigated. The results show that an increasing number of fault planes leads to a reduced peak bending moment ( M max ) and shear force ( V max ). As the number of fault planes increased from one to four, M max and V max decreased by 1.57 times and 3.31 times, respectively. Expanding d corresponds to a reduction in both M max and V max . The minimum V max within the tunnel materializes at xi 4 ( Delta f d1 = Delta f d2 = Delta f d3 ), and the tunnel ' s V max appears at the fault plane of maximum fault displacement. Moreover, with the augmentation of C , an increase in both M max and V max was observed. Additionally, upon attaining a normal fault displacement of 0.2 m, the tunnel lining undergoes both tensile and compressive failure at the fault plane. As the normal fault displacement surpasses 0.4 m, the failure range of the tunnel at the fault plane undergoes a precipitous escalation, marked by a maximum increase of 68.8 % in tensile failure and a 29.6 % increase in compressive failure.

The implementation of stone columns is a widely accepted method for improving the stability of liquefiable soil. A comprehensive understanding of the behavior of the composite ground is crucial for accurate design and calculation in practical applications. Several existing mathematical models were established to assess characteristics of the stone column-improved ground by typically ignoring the vertical seepage within liquefiable soil. This negligence will inevitably lead to significant calculation errors, particularly when the vertical permeability of liquefiable sites is high or the installation spacing of stone columns is large. In this context, a new mathematical model which accounts for coupled radial-vertical seepage within liquefiable soil is proposed to determine the reinforcement performance of stone columns. The equal strain assumption and new boundary conditions are incorporated to obtain numerical solutions with the finite difference method. Then the present solution is degenerated to the conventional calculation model to verify the reasonability of the proposed model. Finally, a parametric analysis is conducted to investigate the impacts of crucial parameters on the performance of stone columns for excess pore water pressure variation during soil liquefaction. The results reveal that the peak value of the maximum excess pore water pressure ratio increases with the increment of both the column spacing and cyclic stress ratio. Moreover, the increasing radial and vertical consolidation parameters Tb and Th will accelerate the dissipation rate of the excess pore water pressure of liquefiable sites. Furthermore, the conventional model neglecting the vertical seepage will underestimate the variation rate of the excess pore water pressure, and the calculation error will become larger with the increase of Th.